1. Field of the Invention
The present invention relates to a solid electrolytic capacitor whose reliability is improved.
2. Description of the Related Art
A solid electrolytic capacitor has an excellent high-frequency characteristic, and in addition to this it is compact and has a large capacity, and therefore it is widely used in high-frequency circuits of various electronic equipment such as personal computers and image equipment.
A cross section structure of a conventional solid electrolytic capacitor is shown in FIG. 3. FIG. 3(a) is a longitudinal sectional view, FIG. 3(b) is a horizontal sectional view, and FIG. 3(c) is a transverse sectional view. An anode body, a dielectric layer and a conductive polymer layer are formed around an anode lead 2. An enlarged sectional view of the anode body and its circumference is shown in FIG. 4. An anode body 3a is formed around the anode lead 2 by sintering particles of valve metal such as tantalum, niobium, titanium or aluminum into a rectangular solid.
A dielectric layer 3b is formed on the surfaces of this anode body 3a and the anode lead 2. The dielectric layer 3b is formed by oxidizing the surfaces of the anode body 3a and the anode lead 2 by, for example, in an anodizing method. A conductive polymer layer 3c is formed to fill above this dielectric layer 3b and a space.
A carbon layer 4 and a silver layer 5 are formed on the surface of the conductive polymer layer 3c. A plate-like anode terminal 1 is connected to the anode lead 2, and a plate-like cathode terminal 6 is connected to the silver layer 5.
A housing 8 is formed into a rectangular shape so as to accommodate the anode lead 2, the anode body 3a, the dielectric layer 3b, the conductive polymer layer 3c, the carbon layer 4 and the silver layer 5. The housing 8 is, for example, composed of an epoxy resin. The anode terminal 1 and the cathode terminal 6 are drawn out of the housing 8 in opposite directions, and are respectively bent downward. Tip portions of these terminals are located along the under surface of the housing 8, and used for electrically connecting the solid electrolytic capacitor to a mounted board as described (for example, see Japanese Unexamined Patent Publication No. 2004-14667).